1. Field of the Invention
The present invention relates to a seat belt system for restraining an occupant in a seat. More specifically, this invention limits the movement of the seat belt webbing relative to the latch plate during normal usage, but permits the seat belt webbing to slide through the latch plate during a collision, thus providing improved restraint to the occupant.
2. Relevant Technology
Seat belts are known to increase the safety of occupants in various motorized vehicles. Seat belt use is often cited as the most useful line of defense in reducing accident related injuries. The actions of consumer groups, governmental agencies, and political activists all reflect the tremendous societal value of seat belt use. Legislation requiring manufacturers to include seat belts in their vehicles has been in place for many years. More recently, laws have been enacted requiring consumers to use seat belts.
The benefits of seat belt use are numerous. In a collision, seat belts may prevent the occupant of a vehicle from striking the interior of the vehicle or other objects within the vehicle, including other occupants. Seat belts aid in keeping the occupant inside the vehicle, where the chances of survival are much greater. Seat belts may also keep the driver behind the wheel and in control of the vehicle in a collision, averting additional damage or injuries. Seat belts also enhance the effectiveness of other safety devices. For example, in a vehicle with airbags, a seat belt keeps the occupant in the seat, so the airbag can better protect the occupant.
Statistics show that lap/shoulder belts, when used properly, reduce the risk of fatal injury in front-seat-car occupants by 45 percent and the risk of moderate-to-critical injury by 50 percent. With respect to light truck occupants, seat belts reduce the risk of fatal injury by 60 percent and moderate-to-critical injury by 65 percent.
Seat belts vary in their configuration, but one of the most common types of seat belts is the lap belt. The lap belt includes right and left belts, which traverse an occupant""s lap and are secured to each other near the occupant""s mid-abdomen. The right and left belts may be secured together by a buckle. Lap belts are found in many different types of vehicles throughout the world.
Although conventional lap belts are well used and accepted, they do not limit movement of an occupant""s head and torso. Thus, although the lower body is restrained, the upper body may experience rapid and dangerous movement during an accident. This is particularly dangerous for passengers in the front seat of an automobile, who may strike the steering wheel, dashboard, or windshield during an accident.
A seat belt having a shoulder strap limits an occupant""s upper body movement in an accident, providing improved and potentially lifesaving restraint. Shoulder-strap restraints come in various configurations, involving both single- and double-strap implementations. In one commonly employed shoulder-strap configuration, the seat belt webbing traverses the occupant""s upper body in a diagonal fashion, passes through a latch plate, and then traverses the occupant""s lap. The latch plate is fastened to a buckle, which is secured to the vehicle, providing restraint to both the occupant""s lower and upper body. This seat belt system is frequently employed in passenger vehicles.
However, in this configuration, problems arise in loading and unloading occupants. Often the latch plate becomes dislocated from its correct position, making it difficult for the occupant to locate the latch plate or correctly position the latch plate before engaging the seat belt.
The dislocation of the latch plate creates a number of safety and convenience issues. For example, the latch plate could move so far from its correct position that it may be difficult for the occupant to locate or secure the latch plate, discouraging the occupant from even using the seat belt. Also, in this condition, the seat belt webbing is more likely to become knotted or entangled with other items around the seat belt. Further, if the latch plate is not in the correct position when in use, the seat belt webbing may have slack, preventing the seat belt from safely restraining the occupant in the event of an accident.
To remedy these problems, web stops, also known as web stop buttons, were developed. A web stop is comprised of two end pieces connected by a crosspiece. The crosspiece passes through the seat belt webbing, an end piece being connected to each end of the crosspiece such that the end pieces are located on opposite sides of the seat belt webbing. The end pieces are large enough that the latch plate cannot pass over the web stop. Thus, the latch plate can move freely until contacting a web stop.
The end pieces are often shaped like disks or buttons, one of the two broadest edges of each of the disks or buttons being connected to the crosspiece. Often, the edges of the end pieces facing away from the crosspiece are rounded so that the web stops have the appearance of a small mound, with a flattened top, sitting on the seat belt webbing.
To keep the latch plate in the proper range, a web stop is often placed on the seat belt webbing, both above and beneath the latch plate. This restriction on the movement of the latch plate maintains the latch plate in the proper position before, during, and after use by an occupant.
While this restriction is desirable in normal usage, it has substantial limitations in the event of an accident. In a collision, the torso of the occupant is often thrust forward, applying great pressure to the torso portion of the seat belt webbing (the portion of the seat belt webbing above the latch plate). The torso portion of the seat belt webbing pulls on the lap portion of the seat belt webbing (the portion of the seat belt webbing below the latch plate) for only a fraction of a second. Then, the web stop below the latch plate makes contact with the latch plate. As conventional web stops are not designed to break away from the seat belt webbing in an accident, no more tension is transferred from the torso portion of the seat belt webbing to the lap portion of the webbing, leaving the lap portion of the seat belt undesirably loose and permitting the occupant""s legs and lower body to be thrown in a dangerous fashion.
In this condition, the occupant""s lower body may strike portions of the vehicle or other objects with great force. Most dangerously, lacking tension in the lap portion of the seat belt webbing, the occupant may slide completely or partially out of the seat belt restraint (this process is known as xe2x80x9csubmariningxe2x80x9d), resulting in potentially more serious injuries. The transfer of tension from the torso portion of the seat belt to the lap portion of the seat belt during an accident is desirable and enhances the restraining capabilities of the seat belt.
Thus, it would be an advancement in the art to provide a web stop that remains in place during normal usage, but separates from the seat belt webbing during a collision.
Such an apparatus is disclosed and claimed herein.
The apparatus of the present invention has been developed in response to the present state-of-the-art, and, in particular, in response to problems and needs in the art that have not yet been fully resolved by currently available seat belt systems. Thus, it is an overall objective of the present invention to provide a breakaway web stop apparatus for enhancing the effectiveness of seat belt restraint systems.
To achieve the foregoing objects, and in accordance with the invention as embodied and broadly described in the preferred embodiment, a breakaway web stop enabling a seat belt system to provide increased restraint is provided. In one such seat belt system, the seat belt webbing may traverse an occupant""s upper body in a diagonal fashion, passing through a webbing orifice in a latch plate, and then crossing over the occupant""s lap. When the seat belt system is in use, the latch plate is secured to a buckle within the vehicle. Frequently, each end of the seat belt webbing is attached to a retractor. In another embodiment, one end of the seat belt webbing is attached to a retractor, and the other end is anchored to the vehicle.
In one embodiment, a conventional web stop or breakaway web stop may be attached to the seat belt webbing slightly above the latch plate, forming an upper boundary for the proper range of the latch plate. A breakaway web stop is attached to the seat belt webbing slightly below the latch plate, forming a lower boundary for the proper range of the latch plate.
As with a conventional web stop, the breakaway web stop contains two end pieces and a crosspiece situated between and connected to two end pieces. The crosspiece of the breakaway web stop also passes through the seat belt webbing, having an end piece on each end of the crosspiece, the end pieces being located on opposite sides of the seat belt webbing. The crosspiece of the breakaway web stop may take on a wide variety of shapes, being, for example, cylindrical or rectangular. A breakaway web stop differs from the conventional web stop in shape and configuration for the purpose of permitting the breakaway web stop to separate from the seat belt webbing upon the application of a specific amount of force.
In one embodiment of the breakaway web stop, there is a notch on the crosspiece. The notch creates a xe2x80x9cweak pointxe2x80x9d within the web stop such that the crosspiece will break at the narrowest point of the crosspiece when the web stop is subjected to the force of an accident. More specifically, in the event of an accident, the torso of the occupant is thrust forward, creating tension in the torso portion of the seat belt. The breakaway web stop located below the latch plate is pulled against the latch plate, and the breakaway web stop separates from the seat belt webbing. This separation allows tension from the torso portion of the seat belt webbing to be transferred to the lap portion of the seat belt webbing, providing superior restraint to the occupant.
By varying the position and characteristics of the notch, the web stop manufacturer can determine the amount of force required to break the web stop. The notch in the crosspiece may be positioned at the midpoint of the crosspiece relative to the two end pieces and may face the latch plate. However, the notch may be positioned elsewhere to vary the force required to break the web stop and the manner in which the web stop separates from the seat belt webbing.
In another embodiment of the breakaway web stop, the crosspiece of the web stop has a narrow portion. The narrow portion is smaller than at least one adjacent portion of the crosspiece. The narrowest point of the crosspiece presents the most likely point of breakage in an accident. In this embodiment, the crosspiece may take on a number of different forms. For example, the crosspiece may gradually or abruptly decrease in size, forming a narrow portion. Again, by altering the characteristics of the crosspiece, the manufacturer can specify the amount of force required to break the web stop. Many combinations satisfy the parameters of this embodiment, as envisioned by the inventors.
Other embodiments alter the configuration of the end pieces, rather than the crosspiece. In one such embodiment, each end piece has angled edges, the angled edges being configured to push at least a portion of the end pieces together as the web stop is pulled into the webbing orifice as a result of an accident. In one embodiment, each end piece also has a leading end, a trailing end, and an interior edge. The interior edge is the edge of the end piece attached to the crosspiece. The leading end is the end of the end piece situated closest to the latch plate when the seat belt system is in use, while the trailing end is the end of the end piece situated farthest from the latch plate. The angled edges converge toward the opposing end piece and the leading end, forming a wedge. When the force of an accident pulls the wedge-shaped web stop against the latch plate, the end pieces, being situated on opposite sides of the seat belt webbing, are pulled into the webbing orifice. As this web stop is pulled further into the webbing orifice and because of the increasing width of the end pieces, at least a portion of the end pieces are toward each other, applying force to the crosspiece. Finally when the pressure is great enough, the crosspiece breaks, freeing the web stop from the seat belt webbing. This breakage may occur by forcing the end pieces to rotate or by simply pushing the end pieces together. To effectuate this operation, each of the leading ends must be sufficiently narrow to simultaneously fit within the webbing orifice, on opposite sides of the seat belt webbing.
Thus, the breakaway web stop, in its various embodiments, maintains the seat belt webbing in the correct position relative to the latch plate during normal usage, but breaks away from the latch plate in an accident, providing increased safety and convenience to its users.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or maybe learned by the practice of the invention as set forth hereinafter.